If it were me, I'd treat all the fish now. Ich is cyclic. The fish only show spots when the parasite is attached to them. When it leaves the fish it begins reproducing then the whole thing starts over but worse because there are many times more parasites and the fish are weakened already.
You need a mature tank, many say a year old, for an anemone. They also need a ton of light of the right wavelength. You will need special lights if you want to keep an anemone.
You won't want to put any more fish in the tank until it has been fallow for a while, I think 12 weeks is normal. After this the ich parasite should be gone. As long as you quarantine each new fish for 4 - 6 weeks before you add them to the tank you should be able to keep it away.